Isoform-specific regulation of cytochrome P450 expression and activity by estradiol in female rats

Abstract

Estradiol (E2) is the major endogenous estrogen, and its plasma concentration increases up to 100-fold during pregnancy in humans. Accumulating evidence suggests that an elevated level of E2 may influence hepatic drug metabolism, potentially being responsible for altered drug metabolism during pregnancy. We characterized effects of E2 on expression and activities of cytochrome P450 enzymes (CYPs) in an in vivo system using rats. To this end, female rats were treated with estradiol benzoate (EB) or known CYP inducers. Liver tissues were obtained after 5 days of treatment, and mRNA and protein expression levels as well as activities of major hepatic CYPs were determined by qRT-PCR, immunoblot, and microsomal assay. E2 increased CYP1A2 expression and activity to a smaller extent than β-naphthoflavone did. E2 also enhanced CYP2C expression (CYP2C6, CYP2C7, and CYP2C12) to levels comparable to those observed by phenobarbital. E2 upregulated CYP3A9 expression, while expression of CYP3A1 was downregulated. Expression of hepatic nuclear receptors (PXR and CAR) and the obligate redox partner of CYPs (POR) was downregulated in EB-treated rats, suggesting their potential involvement in regulation of CYP expression and activity by E2. In summary, in female rats E2 regulates expression of hepatic CYPs in a CYP isoform-specific manner although the directional changes are different from those clinically observed during human pregnancy. Further study is warranted to determine whether the changes in drug metabolism during human pregnancy are attributable to involvement of hormones other than E2.

Regulation of Hepatic Phase II Metabolism in Pregnant Mice

“…Elevated levels of hormones coupled with induction of ERa mRNA may be involved in the regulation of other nuclear receptors. A prior study demonstrated the downregulation of PXR and CAR in estradiol benzoate-treated rats (Choi et al, 2011). In addition, Cyp2b10 (CAR target gene) is induced by estradiol and repressed by progesterone in primary mouse hepatocytes, suggesting divergent regulation of this pathway by sex hormones (Kawamoto et al, 2000).…”

Drug Metabolism and Transport During Pregnancy: How Does Drug Disposition Change during Pregnancy and What Are the Mechanisms that Cause Such Changes?

“…For example, three studies in this issue of Drug Metabolism and Disposition approach the regulation of P450 enzymes by estrogens, progesterone, and their combination (Choi et al, 2013;Dickmann and Isoherranen, 2013;Papageorgiou et al, 2013). Together with past evaluations of regulation of P450 enzymes by estrogens (Choi and Jeong, 2009;Mwinyi et al, 2010;Choi et al, 2011;Koh et al, 2012), these studies clearly show that pregnancyrelated hormones regulate P450 mRNA in vitro. However, as highlighted in the articles, during pregnancy maternal hepatocytes are exposed to a combination of hormones and growth factors that may act in a synergistic or antagonistic manner, and dissecting individual mechanisms and regulators will require more in vivo studies during pregnancy as well as more detailed in vitro studies.…”

Isoform-Specific Regulation of Cytochromes P450 Expression by Estradiol and Progesterone

“…Hepatocytes were treated with vehicle control (ethanol), a female hormone, or one of the known inducers for 72 hours, and P450 activities were determined as previously described elsewhere Choi et al, 2011). Briefly, the media were replaced with fresh media containing one of P450 isoform-selective probe substrates for CYP1A2 (50 mM phenacetin), CYP2A6 (100 mM coumarin), CYP2B6 dmd.aspetjournals.org (100 mM S-mephenytoin), CYP2C9 (100 mM diclofenac), CYP2C19 (100 mM S-mephenytoin), CYP2D6 (60 mM bufuralol), CYP2E1 (100 mM p-nitrophenol), and CYP3A4 (15 mM midazolam) and sampled at various time points (30 minutes to 4 hours).…”

“…Separation was performed with a Zorbax Eclipse XDB-C8 column (4.6 Â 50 mm, 3.5 mm) (Agilent Technologies, Santa Clara, CA) except for acetaminophen and 7-hydroxycoumarin (YMC C8 4.6 Â 150 mm, 3.5 mm, Waters, Milford, MA). The quantitative analytical conditions for the metabolites (e.g., internal standards, MRM pairs, and mobile phase gradients) have been previously described Choi et al, 2011).…”